Among nitride semiconductor substrates, GaN substrates have been drawing attention as substrates for manufacturing semiconductor devices such as a light emitting device and an electronic device. However, at present, for manufacturing of a GaN substrate, growth has to be performed on a heterogeneous substrate. Since lattice constant and thermal expansion coefficient are different between the heterogeneous substrate and the GaN crystal, a multiplicity of crystal defects are generated in the GaN crystal, disadvantageously.
To address this, for example, Non-Patent Document 1 discloses a GaN substrate, wherein a GaN crystal provided with a multiplicity of dot-shaped depressions in its surface is grown such that crystal defects are located intensively at the centers of the depressions in the GaN crystal and crystal defects are reduced around the depressions.